It has been known for many years that cannabis shows a variety of psychotropic actions or analgesic actions and it was shown clearly in the 1960s that such actions are caused by a series of compounds (cannabinoid) centering on e-tetrahydrocannabinol (Δ9-THC). At the beginning of the 1990s, two kinds of cannabinoid receptors (CB1 and CB2) were found out as a receptor to which Δ9-THC binds, and also at 1992, N-arachidonoyl ethanolamine (anandamide; AEA) as an endogenous cannabinoid was found from a brain of pig. Anandamide is known to be metabolized mainly by FAAH. Also it has been known that in addition to anandamide, fatty acid amides such as palmitoylethanolamide (PEA), oleylethanolamide (OEA) and oleamide, 2-arachidonoylglycerol (2-AG) and the others are hydrolyzed by FAAH. It has been shown clearly that amounts of these fatty acid amides including anandamide are increased in FAAH knockout mouse, but interestingly it hasn't been acknowledged side effects that are observed in the case of CB1 receptor agonist such as catalepsy, hypothermia, hypomotility and overeating (for example, see Non-Patent Literature-1). Also since the above-mentioned side effects are not observed even at administrating of a FAAH inhibitor, the FAAH inhibitor is expected to be a therapeutic medicament with few side effects compared with CB1 receptor agonist. In fact, it has been reported that the FAAH inhibitor shows an efficacy on pains (neuropathic pain, inflammatory pain, nociceptive pain), anxiety disorder and depression in animal models (for example, see Non-Patent Literature-2). In addition, it has been known that FAAH and fatty acid amides as a substrate are related to various diseases. For example, it has been known that FAAH is increased in a brain of Alzheimer's patient, OEA is related to a feeding regulation, and oleamide is related to an induction of sleeping (for example, see Non-Patent Literature-3), and it has also been reported that the FAAH inhibitor shows a cerebro- and neuro-protective effect as well as a therapeutic effect on thamuria and urinary incontinence, and a therapeutic effect on over active bladder.
A low-molecular compound showing the FAAH inhibitory activity has been reported for example, 4,5-diphenyl imidazole derivatives (for example, see Patent Literature-1), dioxane-2-alkylcarbamic acid derivatives (for example, see Patent Literature-2), O-aryl-N-alkyl carbamic acid aryl ester derivatives (for example, see Patent Literature-3), α-ketoheterocycle derivatives (for example, see Patent Literature-4), biarylether urea derivatives (for example, see Patent Literature-5), triazolopyridine (or pyrimidine)carboxamide derivatives (for example, see Patent Literatures-6, 7) and a low-molecular compound showing the CB1 receptor-binding activity has been also reported for example, benzimidazolone carboxamide derivatives (for example, see Patent Literature-8). But there is neither a description of the present compound having 8-oxodihydropurine structure represented by the below-mentioned formula (1) nor a suggestion of the present compound in these related art documents.